The House of Lords last night threw out controversial plans to site a supercasino in Manchester, despite Tessa Jowell's last-ditch attempt to win back support with a package of concessions.

A fatal amendment - passed by three votes - forced the culture secretary's gambling reforms back to the drawing board, rejecting 16 smaller venues as well as the Las Vegas-style casino.

The government needed majorities in both houses, rendering its 24-vote victory in a simultaneous Commons division worthless. "Ministers will want to reflect and come back to this elected house in due course with proposals as to how to take this policy forward," said the culture secretary, who had previously warned there was "no plan B".

MPs suggested she would have to separate the casinos, allowing the less contentious local venues to proceed, because she cannot bring back the same order for six months.

But isolating the decision on the supercasino could intensify arguments over its location and regulation. Finding parliamentary time for one or both issues could also be difficult: the house rises for recess today and on its return enters "purdah" - where it cannot discuss political decisions which are sensitive locally - before the May council elections.

Labour's leadership transition is likely to begin shortly afterwards and MPs believe Gordon Brown is not keen to see an expansion of the gambling industry, citing the 50% tax rate he introduced for the largest casinos in last week's budget.

The decision to site the supercasino in Manchester was made by an independent panel, but angered MPs in Blackpool, which had bid for the venue, and came under fire after a Lords committee questioned whether its social impact and effect on economic regeneration could be monitored. Opponents argued that a joint committee of both houses should reconsider the panel's choice of location. Other critics were concerned about the risks of gambling addiction.

Last night's vote was only the third time the upper chamber has rejected a government order, prompting speculation that ministers had concentrated too heavily on wooing backbench MPs and had not paid enough attention to the Lords.

Others claimed that Lord Davies of Oldham, speaking for the government, had undermined its case by appearing to suggest that it was accepting a rival amendment only in spirit.

Only 105 Labour peers - around half the party's total - backed the order, with 12 rebelling by voting for the Liberal Democrat amendment. It was also backed by around 30 Tories, who were granted a free vote. "Ultimately, this is a triumph for parliament and will ensure public confidence in its scrutiny function and ability to hold the government to account," said Lord Clement-Jones, who tabled the amendment.

Earlier, Ms Jowell had offered Blackpool MPs a regeneration taskforce and promised to set up a joint committee to look at whether it should be the prime candidate for a supercasino in the next parliament. She told MPs the committee should look at the lessons of the process of the siting of the casinos, but said it would not be able to rescind the licence for Manchester.

Mr Caborn accused Conservatives of opportunism for voting against the order despite supporting the proposal for a supercasino in last year's gambling bill.

But the shadow culture secretary, Hugo Swire, insisted: "Our priority has always been ensuring that we minimise the effects of gambling addiction, yet the government was more concerned with forcing through this legislation. It would be unthinkable for the government to attempt to bring back these same proposals."